Process for producing (meth)acrolein and/or (meth)acrylic acid

ABSTRACT

A method for producing (meth)acrolein and/or (meth)acrylic acid by subjecting isobutylene and the like or propylene to a vapor-phase catalytic oxidation with molecular oxygen in the presence of a solid oxidation catalyst in a tubular type of fixed bed reactor, wherein a temperature of a hot-spot zone is sufficiently controlled and (meth)acrolein and (meth)acrylic acid are produced with a high yield. 
     A method for producing (meth)acrolein and/or (meth)acrylic acid by passing a raw material gas comprising isobutylene and the like or propylene and oxygen through a catalyst layer in a tubular type of fixed bed reactor which is filled with a solid oxidation catalyst, which includes passing a gas containing isobutylene and the like or propylene in a concentration lower than that of the raw material gas, and oxygen through the catalyst layer for a period of one hour or more prior to passing the raw material gas through the catalyst layer.

TECHNICAL FIELD

The present invention relates to a method of producing methacroleinand/or methacrylic acid, which comprises subjecting isobutylene and/ortertiary butanol to a vapor-phase catalytic oxidation with molecularoxygen in the presence of a solid oxidation catalyst by employing atubular type of fixed bed reactor.

The present invention also relates to a method of producing acroleinand/or acrylic acid, which comprises subjecting propylene to vapor-phasecatalytic oxidation with molecular oxygen in the presence of a solidoxidation catalyst by employing a tubular type of fixed bed reactor.

BACKGROUND ART

With respect to a catalyst which is used when isobutylene and/ortertiary butanol are subjected to a vapor-phase catalytic oxidation soas to produce methacrolein and/or methacrylic acid, and a catalyst whichis used when propylene is subjected to a vapor-phase catalytic oxidationso as to produce acrolein and/or acrylic acid, a number of proposalshave been made. These proposals relate primarily to elementsconstituting the catalyst and to the ratios thereof.

The above vapor-phase catalytic oxidation is an exothermic reaction,which causes thermal storage in a catalyst layer. A high temperaturelocal zone which results from the thermal storage is referred to as a“hot-spot”. An excessive high temperature of this zone causes excessiveoxidation, whereby the yield of an object product is decreased.Therefore, in the industrial operation of the above oxidation, theinhibition of the temperature of a hot-spot is a serious problem. Inparticular, when concentrations of isobutylene and/or tertiary butanol(which may be referred to as “isobutylene and the like”) or propylene ina raw material gas are increased so as to increase the productivity, thetemperature of a hot-spot tends to be elevated, and therefore, reactionconditions therefor are actually subjected to large constraints.

Therefore, in order to industrially produce (meth)acrolein and/or(meth)acrylic acid with a high yield, it is very important to controlthe temperature of a hot-spot zone. Furthermore, in particular, when asolid oxidation catalyst including molybdenum is used, it is importantto prevent a generation of the hot-spot because the molybdenum componentis apt to easily sublimate.

Additionally, the term “(meth)acrolein” means “methacrolein and/oracrolein”, and the term “(meth)acrylic acid” means “methacrylic acidand/or acrylic acid”.

Heretofore, several methods of controlling the temperature of a hot-spotzone have been proposed. For example, JP-A-3-176440 discloses a methodwhich comprises filling a reactor with a plural kinds of catalysts,which are different from each other on activities and have been preparedby varying their compositions, so that the activities are increasinglyenhanced from the inlet side of a raw material gas toward the outletside thereof, and passing a raw material gas including oxygen,isobutylene and the like through the catalysts layer. JP-A-55-113730discloses a method which comprises filling a reactor with a plural kindsof catalysts, which are different from each other on activities and havebeen prepared by varying their compositions, so that the activities areincreasingly enhanced from the inlet side of a raw material gas towardthe outlet side thereof, and passing a raw material gas including oxygenand propylene through the catalysts layer. JP-A-8-92147 discloses amethod which comprises controlling a flow of a heating medium so that atemperature of a heating medium bath be elevated by 2° C. to 10° C.between the inlet port of a multi-tubular type of fixed bed reactorhaving the heating medium bath and the outlet port thereof, whenpropylene is subjected to a vapor-phase oxidation into acrolein by usingthe reactor.

Each of these methods is the one in which the rate of reaction per unitvolume at an inlet side for a raw material gas in a catalyst layerwithin a reactor is lowered so as to control a calorific value ofreaction per unit volume, so that the temperature of a hot-spot zone canbe lowered.

Furthermore, JP-A-2001-55355 discloses a method of producing anunsaturated nitrile and/or an unsaturated carboxylic acid, whichcomprises subjecting a hydrocarbon to a-vapor-phase catalytic oxidationin the presence of a compound metal-oxide catalyst including, as anessential ingredient(s), molybdenum, vanadium, and at least one elementselected from the group consisting of tellurium and antimony, whereinthe temperature is elevated in an atmosphere in which oxygen and/or acombustible gas are substantially included, until the temperature of thecatalyst layer reaches a temperature at which a reaction can beinitiated. Besides, in comparative example of the specification thereof,a method of elevating the temperature in an atmosphere of air is alsodisclosed.

DISCLOSURE OF INVENTION

However, there has been a problem that the temperature of a hot-spotzone can not be sufficiently controlled by merely these methods and theyield of each of (meth)acrolein and (meth)acrylic acid is low.

It is an object of the present invention to provide a method forproducing (meth)acrolein and/or (meth)acrylic acid by subjectingisobutylene and the like or propylene to a vapor-phase catalyticoxidation with molecular oxygen in the presence of a solid oxidationcatalyst in a tubular type of fixed bed reactor, whereby a temperatureof a hot-spot zone is sufficiently controlled and (meth)acrolein and(meth)acrylic acid are produced with a high yield.

The present invention provides a method for producing (meth)acroleinand/or (meth)acrylic acid by passing a raw material gas comprisingisobutylene and the like or propylene and oxygen through a catalystlayer in a tubular type of fixed bed reactor which is filled with asolid oxidation catalyst, which comprises passing a gas comprisingisobutylene and the like or propylene in a concentration lower than thatof said raw material gas, and oxygen through said catalyst layer for aperiod of one hour or more prior to passing said raw material gasthrough said catalyst layer.

In particular, the present invention also provides a method forproducing (meth)acrolein and/or (meth)acrylic acid, which comprises:

filling a tubular type of fixed bed reactor with a solid oxidationcatalyst;

elevating a temperature of the resultant catalyst layer to a range of250° C. to 400° C. while passing a gas including oxygen, nitrogen, watervapor and 0 to 0.5% by volume of isobutylene and the like or propylenethrough said catalyst layer; and

passing a gas including 1 to 3.8% by volume of isobutylene and the likeor propylene, 7 to 16% by volume of oxygen and 5 to 50% by volume ofwater vapor through said catalyst layer at a temperature of 250° C. to400° C. for a period of one hour or more; and thereafter passing a rawmaterial gas including 4 to 9% by volume of isobutylene and the like orpropylene, 7 to 16% by volume of oxygen and 5 to 50% by volume of watervapor through said catalyst layer at a temperature of 250° C. to 400° C.

In the present invention, a reaction for synthesizing (meth)acroleinand/or (meth)acrylic acid is carried out by using a tubular type offixed bed reactor. The tubular type of fixed bed reactor is industriallyand preferably, but not in particular limited to, a multi-tubular typeof fixed bed reactor which is provided with several thousands to severaltens thousand of reaction tubes having an inner diameter of 10 to 40 mm.Furthermore, the tubular type of fixed bed reactor is preferably the oneas provided with a heating medium bath. The heating medium is not inparticular limited, and includes salt melts such as potassium nitrateand sodium nitrite.

In the present invention, a solid oxidation catalyst to be used is notin particular limited, provided that the catalyst is a solid catalystfor this oxidation reaction, and a compound oxide including molybdenumwhich has been conventionally known and the like can be used therefor.For a reaction wherein isobutylene and the like are used as rawmaterials, a compound oxide as represented by the following formula (1):Mo_(a)Bi_(b)Fe_(c)A_(d)X_(e)Y_(f)Z_(g)O_(h)  (1)wherein Mo, Bi, Fe and O represent molybdenum, bismuth, iron and oxygen,respectively; A represents nickel and/or cobalt; X represents at leastone element selected from the group consisting of magnesium, zinc,chromium, manganese, tin and lead; Y represents at least one elementselected from the group consisting of phosphorus, boron, sulfur,tellurium, silicon, germanium, cerium, niobium, titanium, zirconium,tungsten and antimony; Z represents at least one element selected fromthe group consisting of potassium, sodium, rubidium, cesium andthallium; and each of a, b, c, d, e, f, g and h represents an atomicratio of each element, wherein 0.1≦b≦5, 0.1≦c≦5, 1≦d≦12, 0≦e≦10, 0≦f≦10and 0.01≦g≦3 when a=12, and h means an atomic ratio of oxygen necessaryto satisfy the atomic valence of each of said elements, is preferred asa catalyst. A particularly preferred atomic ratio of each element is0.2≦b≦3, 0.5≦c≦4, 2≦d≦10 and 0.1≦g≦2 when a=12.

Besides, for a reaction wherein propylene is used as a raw material, acompound oxide as represented by the following formula (2):Mo_(a′)Bi_(b′)Fe_(c′)A′_(d′)X′_(e′)Y′_(f′)Z′_(g′)Si_(h′)O_(i)  (2)wherein Mo, Bi, Fe, Si and O represent molybdenum, bismuth, iron,silicon and oxygen, respectively; A′ represents nickel and/or cobalt; X′represents at least one element selected from the group consisting ofmagnesium, zinc, chromium, manganese, tin, strontium, barium, copper,silver and lead; Y′ represents at least one element selected from thegroup consisting of phosphorus, boron, sulfur, tellurium, aluminum,gallium, germanium, indium, lanthanum, cerium, niobium, tantalum,titanium, zirconium, tungsten and antimony; Z′ represents at least oneelement selected from the group consisting of potassium, sodium,rubidium, cesium and thallium; each of a′, b′, c′, d′, e′, f′, g′, h′and i represents an atomic ratio of each element, wherein 0.01≦b′≦5,0.01≦c′≦5, 1≦d′≦12, 0≦e′≦10, 0≦f′≦10, 0.001≦g′≦3 and 0≦h′≦20 when a′=12,and i means an atomic ratio of oxygen necessary to satisfy the atomicvalence of each of said elements, is preferred as a catalyst. Aparticularly preferred atomic ratio of each element is 0.1≦b′≦3,0.1≦c′≦4, 2≦d′≦10 and 0.005≦g′≦2 when a′=12.

A method of preparing the catalyst to be used in the present inventionis not in particular limited, and various methods as conventionally wellknown can be used, provided that components do not cause remarkablemaldistribution.

Raw materials as used for preparing the catalyst are not in particularlimited, and a nitrate, a carbonate, an acetate, an ammonium salt, anoxide and a halide and the like of each element can be used incombination to each other. For example, as a molybdenum raw material,ammonium paramolybdate, molybdenum trioxide, molybdenum chloride or thelike can be used.

The catalyst used in the present invention can be used with no carrier,while the catalyst can be used in the form of a supported catalyst whichis supported on an inactive carrier such as silica, alumina, asilica-alumina, or silicon-carbide, or in the form of a catalyst dilutedwith such an inactive carrier.

In the present invention, the term “a catalyst layer” means a space zonein a reaction tube of a tubular type of fixed bed reactor, whichincludes at least a catalyst; that is to say, not only a space which isfilled with merely a catalyst but also a space in which a catalyst isdiluted with an inactive carrier or the like are referred to as “acatalyst layer”. However, a space at each end as filled with nothing, ora space as filled with merely an inactive carrier or the like are notreferred to as “a catalyst layer”, because no catalyst is substantiallyincluded therein.

A reaction for synthesizing (meth)acrolein and/or (meth)acrylic acid,which comprises subjecting isobutylene and the like or propylene tovapor-phase catalytic oxidation with molecular oxygen in the presence ofa solid oxidation catalyst by employing a tubular type of fixed bedreactor, which is simply referred to as “an oxidation reaction”, ispreferably carried out at a reaction temperature in the range of 250° C.to 400° C. However, when a raw material gas including, for example, 4 to9% by volume of isobutylene and the like or propylene, 7 to 16% byvolume of oxygen, and 5 to 50% by volume of water vapor, which is simplyreferred to as “a raw material gas”, is passed from the initiation ofreaction through a catalyst layer whose temperature is maintained at areaction temperature of about 250° C. to about 400° C., a hot-spothaving a high maximum temperature tends to be formed near a raw materialgas inlet port of the catalyst layer.

The present inventor has made extensive studies to solve this problem.As a result, it has been found that according to a method for producing(meth)acrolein and/or (meth)acrylic acid by passing a raw material gascomprising isobutylene and the like or propylene, and oxygen through acatalyst layer in a tubular type of fixed bed reactor which is filledwith a solid oxidation catalyst, which comprises passing a gascomprising isobutylene and the like or propylene in a concentrationlower than that of said raw material gas, and oxygen through saidcatalyst layer for a period of one hour or more prior to passing saidraw material gas through said catalyst layer, when an oxidation reactionis carried out under usual reaction conditions, a temperature of ahot-spot zone can be sufficiently controlled, and as a result,(meth)acrolein and/or (meth)acrylic acid can be produced with a highyield.

In particular, according to a method which comprises elevating atemperature of the catalyst layer to a temperature of 250° C. to 400° C.while passing a gas comprising oxygen, nitrogen, water vapor and 0 to0.5% by volume of isobutylene and the like or propylene through saidcatalyst layer; and passing a gas comprising 1 to 3.8% by volume ofisobutylene and the like or propylene, 7 to 16% by volume of oxygen and5 to 50% by volume of water vapor at a temperature of 250° C. to 400° C.through said catalyst layer for a period of one hour or more, prior topassing the above raw material gas through the catalyst layer, when anoxidation reaction is carried out under usual reaction conditions, thatis, at a reaction temperature of 250° C. to 400° C. using the above rawmaterial gas, the temperature of the hot-spot zone can be in particularsufficiently controlled.

A temperature of the catalyst layer before elevating the temperature ofthe catalyst layer to the range of 250° C. to 400° C., that is, thetemperature at which the temperature-elevation is started is not inparticular limited, but is preferably in the range of 10° C. to 240° C.Furthermore, a temperature-elevation rate also is not in particularlimited, but is preferably in the range of 10 to 500° C./hour,particularly 20 to 400° C./hour.

A passing gas which is passed for elevating the temperature of thecatalyst layer to the range of 250° C. to 400° C. is a gas comprisingisobutylene and the like or propylene, and oxygen, preferably comprising0 to 0.5% by volume of isobutylene and the like or propylene, oxygen,nitrogen and water vapor. The concentrations of oxygen, nitrogen andwater vapor in this gas are not in particular limited, but preferably,oxygen is in the range of 1 to 21% by volume, nitrogen is in the rangeof 29 to 98.5% by volume, and water vapor is in the range of 0.5 to 50%by volume. Besides, isobutylene and the like or propylene is in therange of 0 to 0.5% by volume, preferably 0 to 0.3% by volume, and inparticular preferably 0 to 0.1% by volume. When a gas comprisingisobutylene and the like or propylene in an amount exceeding 0.5% byvolume is passed with the temperature of the catalyst layer lower than250° C., compounds having a relatively high boiling point which isproduced on the catalyst may poison active sites of the catalyst.Incidentally, the wording “the concentration of isobutylene and thelike” means the sum of the concentration of each of isobutylene andtertiary butanol. This passing gas can include other gases in additionto oxygen, nitrogen, water vapor, and isobutylene and the like orpropylene. As such other gases, for example, an inert gas such as carbondioxide, lower saturated aldehyde, and ketone and the like can beenumerated. However, when an organic compound such as lower saturatedaldehyde is included, the sum of the concentration of each ofisobutylene and the like or propylene and other organic compounds ispreferably 0.5% by volume or less. When the temperature of the catalystlayer is elevated, the flow rate of the passing gas is not particularlylimited; however, such a flow rate to provide a space velocity of 100 to2000 hours⁻¹ is preferred. In this case, the internal pressure of thereactor is usually from atmospheric pressure to several atmosphericpressure.

The above gas which is passed through the catalyst layer after elevatingthe temperature of the catalyst layer is the one including 1 to 3.8% byvolume of isobutylene and the like or propylene, 7 to 16% by volume ofoxygen and 5 to 50% by volume of water vapor. The concentration ofisobutylene and the like or propylene is preferably in the range of 1 to3% by volume, and in particular preferably 1 to 2.5% by volume; theconcentration of oxygen is preferably in the range of 7.5 to 14% byvolume, and in particular preferably 8 to 12% by volume; and theconcentration of water vapor is preferably in the range of 2 to 40% byvolume, and in particular preferably 4 to 30% by volume. When this gasis passed, the temperature of the gas is in the range of 250 to 400° C.Furthermore, a period of time during which the gas is passed is one houror more, preferably 1.5 to 100 hours, and in particular preferably 2 to50 hours. This gas can include other gases in addition to oxygen, watervapor, and isobutylene and the like or propylene. As such other gases,for example, nitrogen, carbon dioxide, lower saturated aldehyde, andketone and the like can be enumerated. The flow rate of the gas which ispassed after elevating the temperature of the catalyst layer is notparticularly limited; however, such a flow rate to provide a spacevelocity of 100 to 3000 hour⁻¹ is preferred. In this case, the internalpressure of the reactor is usually from atmospheric pressure to severalatmospheric pressure. When the gas is passed, a hot-spot zone having alow maximum temperature is formed over a large area.

Thereafter, when an oxidation reaction is carried out under the abovereaction conditions, that is, at a reaction temperature of 250 to 400°C. using a raw material gas including 4 to 9% by volume of isobutyleneand the like or propylene, the maximum temperature of the hot-spot zoneis in particular restrained. As a result, sequential oxidation on thehot-spot zone is in particular restrained, whereby (meth)acrolein and(meth)acrylic acid can be produced with a high yield. The flow rate ofthe raw material gas is not particularly limited; however, such a flowrate to provide a space velocity of 300 to 3000 hour⁻¹, particularly 500to 2000 hour⁻¹, is preferred. The reaction temperature for the oxidationreaction is preferably in the range of 250° C. to 400° C., and inparticular preferably in the range of 280° C. to 380° C. Besides, thereaction pressure is usually from atmospheric pressure to severalatmospheric pressure.

When the present invention is carried out, it is economicallyadvantageous to use air as an oxygen source for the raw material gas,the gas which is passed on elevating the temperature of a catalystlayer, and the gas which is passed after elevating the catalyst layertemperature.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples will be enumerated hereinafter to more particularly explain thepresent invention. Incidentally, the unit “part(s)” in Examples andComparative Examples means “part(s) by mass”. The composition of acatalyst was calculated from the amounts of charged raw materials ofcatalyst components. As a heating medium for a reactor, a salt meltcomprising 50% by mass of potassium nitrate and 50% by mass of sodiumnitrite was used. A hot-spot was detected from ΔT of a catalyst layer(i.e., the temperature of the catalyst layer minus the temperature of aheating medium bath).

A temperature within the catalyst layer was measured by using athermocouple inserted in a protective tube which was located at a centerof a cross-section perpendicular to a tube axial direction of a reactiontube. Additionally, the inside of the protective tube was separated froma system of reaction, while the position of temperature measurementcould be shifted by adjusting the length of the thermocouple as insertedthereinto.

The analyses of a raw material gas and a product gas of reaction werecarried out by means of gas chromatography.

In addition, the rate of reaction of isobutylene and the like orpropylene, the selectivity factors of produced (meth)acrolein and(meth)acrylic acid, and the yield of (meth)acrolein and (meth)acrylicacid are defined as follows, respectively:

Rate of reaction of isobutylene and the like or propylene (%)=(B/A)×100;

Selectivity factor of (meth)acrolein (%)=(C/B)×100;

Selectivity factor of (meth)acrylic acid (%)=(D/B)×100; and

Yield of (meth)acrolein and (meth)acrylic acid (%)={(C+D)/A)}×100,

wherein A represents the number of moles of fed isobutylene and the likeor propylene; B represents the number of moles of reacted isobutyleneand the like or propylene; C represents the number of moles of produced(meth)acrolein; and D represents the number of moles of produced(meth)acrylic acid.

EXAMPLE 1

To 1000 parts of water, 500 parts of ammonium paramolybdate, 18.5 partsof ammonium paratungstate, 18.4 parts of cesium nitrate and 354.5 partsof silicasol of 20% by mass were added, heated and agitated (Liquid A).Aside from this, to 850 parts of water, 250 parts of nitric acid of 60%by mass were added and homogenized, and then 57.2 parts of bismuthnitrate was added thereto and dissolved. To the mixture, 238.4 parts offerric nitrate, 4.7 parts of chromium(III) nitrate, 411.8 parts ofnickel(II) nitrate and 60.5 parts of magnesium nitrate were sequentiallyadded, and dissolved (Liquid B). Liquid B was added to Liquid A into aslurry, and then 34.4 parts of antimony trioxide were added thereto andheated and agitated, so that most of water was evaporated. The resultantcaked matter was dried at a temperature of 120° C., and then calcined ata temperature of 500° C. for a period of six hours. To 100 parts of theresultant calcined product, 2 parts of graphite were added, which werethen formed into rings having an outer diameter of 5 mm, an innerdiameter of 2 mm and a length of 5 mm by using a tablet forming machine,whereby Catalyst 1 was obtained. The elementary composition of Catalyst1 comprised Mo₁₂Bi_(0.5)Fe_(2.5)Ni₆Mg₁Cr_(0.05)W_(0.3)Sb₁Si₅Cs_(0.4),except oxygen.

The temperature of a heating medium bath of a tubular type of fixed bedsteel reactor having an inner diameter of 25.4 mm with the heatingmedium bath was set to a temperature of 180° C., and an inlet side forraw material gas was filled with a mixture of 620 ml of Catalyst 1 and130 ml of a spherical alumina having an outer diameter of 5 mm, while anoutlet side was filled with 750 ml of Catalyst 1, wherein the length ofa catalyst layer was 3005 mm.

The heating medium bath temperature was elevated to a temperature of340° C. at a rate of 50° C./hour, while a gas comprising 9% by volume ofoxygen, 10% by volume of water vapor and 81% by volume of nitrogen waspassed through this catalyst layer at a space velocity of 240 hour⁻¹.

Then, with the heating medium bath temperature maintained at atemperature of 340° C., a gas (i. e., a passing gas after elevating thetemperature) comprising 2% by volume of isobutylene, 8% by volume ofoxygen, 15% by volume of water vapor and 75% by volume of nitrogen waspassed through the catalyst layer at a space velocity of 1000 hours⁻¹for a period of three hours.

Subsequently, with the heating medium bath temperature maintained at atemperature of 340° C., a raw material gas comprising 5% by volume ofisobutylene, 12% by volume of oxygen, 10% by volume of water vapor and73% by volume of nitrogen was passed through the catalyst layer at areaction temperature (i. e., a heating medium bath temperature) of 340°C. at a space velocity of 1000 hour⁻¹. When the temperatures of thecatalyst layer were measured at this time, a hot spot having a maximumtemperature was observed at a site located 500 mm apart from the end ofthe inlet side for the raw material gas, wherein ΔT at the maximumtemperature was 33° C. In addition, the rate of reaction of isobutylenewas 95.5%, the selectivity factor of methacrolein was 85.7%, theselectivity factor of methacrylic acid was 3.6%, and the yield ofmethacrolein and methacrylic acid was 85.3%.

EXAMPLE 2

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of a passing gas after elevatingthe temperature was changed to the one comprising 2.6% by volume ofisobutylene, 8% by volume of oxygen, 15% by volume of water vapor and74.4% by volume of nitrogen. As a result, a hot spot having a maximumtemperature was observed at a site located 470 mm apart from the end ofthe raw material gas inlet side of a catalyst layer, wherein ΔT at themaximum temperature was 35° C. In addition, the rate of reaction ofisobutylene was 95.6%, the selectivity factor of methacrolein was 85.4%,the selectivity factor of methacrylic acid was 3.6%, and the yield ofmethacrolein and methacrylic acid was 85.1%.

EXAMPLE 3

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the time for passing the passing gas afterelevating the temperature was changed to 1.5 hours. As a result, a hotspot having a maximum temperature was observed at a site located 470 mmapart from the end of the raw material gas inlet side of a catalystlayer, wherein ΔT at the maximum temperature was 35° C. In addition, therate of reaction of isobutylene was 95.7%, the selectivity factor ofmethacrolein was 85.3%, the selectivity factor of methacrylic acid was3.6%, and the yield of methacrolein and methacrylic acid was 85.1%.

COMPARATIVE EXAMPLE 1

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the temperature of a heating medium bath waselevated to 340° C. without passing the passing gas after elevating thetemperature, and except that thereafter a raw material gas wasimmediately passed through the catalyst layer. As a result, a hot spothaving a maximum temperature was observed at a site located 400 mm apartfrom the end of the raw material gas inlet side of the catalyst layer,wherein ΔT at the maximum temperature was 45° C. In addition, the rateof reaction of isobutylene was 94.3%, the selectivity factor ofmethacrolein was 83.1%, the selectivity factor of methacrylic acid was3.7%, and the yield of methacrolein and methacrylic acid was 81.9%.

COMPARATIVE EXAMPLE 2

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the time for passing the passing gas afterelevating the temperature was changed to ten minutes. As a result, a hotspot having a maximum temperature was observed at a site located 400 mmapart from the end of the raw material gas inlet side of the catalystlayer, wherein ΔT at the maximum temperature was 44° C. In addition, therate of reaction of isobutylene was 94.4%, the selectivity factor ofmethacrolein was 83.2%, the selectivity factor of methacrylic acid was3.7%, and the yield of methacrolein and methacrylic acid was 82.0%.

COMPARATIVE EXAMPLE 3

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 4.5% byvolume of isobutylene, 12% by volume of oxygen, 10% by volume of watervapor and 73.5% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of a catalyst layer, wherein ΔTat this maximum temperature was 45° C. In addition, the rate of reactionof isobutylene was 94.3%, the selectivity factor of methacrolein was83.1%, the selectivity factor of methacrylic acid was 3.7%, and theyield of methacrolein and methacrylic acid was 81.9%.

COMPARATIVE EXAMPLE 4

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 0.6% byvolume of isobutylene, 8% by volume of oxygen, 15% by volume of watervapor and 76.4% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of the catalyst layer, wherein ΔTat this maximum temperature was 44° C. In addition, the rate of reactionof isobutylene was 94.4%, the selectivity factor of methacrolein was83.2%, the selectivity factor of methacrylic acid was 3.7%, and theyield of methacrolein and methacrylic acid was 82.0%.

COMPARATIVE EXAMPLE 5

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of the gas as passed when thetemperature of a heating medium bath was elevated to 340° C. was changedto the one comprising 2% by volume of isobutylene, 8% by volume ofoxygen, 15% by volume of water vapor and 75% by volume of nitrogen. As aresult, a hot spot having a maximum temperature was observed at a sitelocated 550 mm apart from the end of the raw material gas inlet side ofa catalyst layer, wherein ΔT at this maximum temperature was 31° C. Inaddition, the rate of reaction of isobutylene was 92.2%, the selectivityfactor of methacrolein was 85.8%, the selectivity factor of methacrylicacid was 3.4%, and the yield of methacrolein and methacrylic acid was82.2%. From the results, it is considered that the catalyst was poisonedwhen the temperature thereof was elevated, because ΔT at the hot spotwas decreased as compared to the one in Example 1 while the rate ofreaction of isobutylene also was decreased.

EXAMPLE 4

To 400 parts of water, 42 parts of 60% nitric acid were added to form ahomogeneous solution, to which 68.7 parts of bismuth nitrate was thenadded and dissolved. 102.9 parts of nickel nitrate and 24.1 parts ofantimony trioxide were sequentially added thereto. To this mixed liquid,165 parts of 28% aqueous ammonia was added so as to obtain a whiteprecipitate and a blue supernatant. These were heated and agitated so asto evaporate most of water. The resultant slurry was dried at atemperature of 120° C. for a period of 16 hours, and then heat-treatedat a temperature of 750° C. for a period of two hours, and pulverized soas to obtain fine powder of a bismuth-nickel-antimony compound.

To 1000 parts of water, 500 parts of ammonium paramolybdate, 12.3 partsof ammonium paratungstate and 23.0 parts of cesium nitrate were added,heated and agitated (Liquid C). Aside from this, to 700 parts of water,230.8 parts of ferric nitrate, 418.9 parts of cobalt nitrate and 60.5parts of magnesium nitrate were sequentially added and dissolved (LiquidD). Liquid D was added to Liquid C to form a slurry, to which 425.5parts of 20% silica-sol and the above-mentioned bismuth-nickel-antimonycompound fine powder were then added, heated and agitated, so that mostof water was evaporated. The resultant caked matter was dried at atemperature of 130° C., and then calcined at a temperature of 300° C. inan air atmosphere for a period of one hour, and pulverized. To 100 partsof the resultant pulverized product, 2 parts of graphite were added andmixed. The mixture were formed into rings having an outer diameter of 5mm, an inner diameter of 2 mm and a length of 3 mm by using a tabletforming machine. This formed tablet product was calcined at atemperature of 520° C. for a period of three hours while air was passed,whereby Catalyst 2 was obtained. The elementary composition of Catalyst2 comprisedMo₁₂W_(0.2)Bi_(0.6)Fe_(2.4)Sb_(0.7)Ni_(1.5)Co_(6.1)Mg_(1.0)Cs_(0.5)Si_(6.0)by an atomic ratio except oxygen.

The temperature of a heating medium bath of a tubular type of fixed bedsteel reactor having an inner diameter of 25.4 mm as provided with theheating medium bath was set to a temperature of 180° C., and the inletside for raw material gas was filled with a mixture of 620 ml ofCatalyst 2 and 130 ml of a spherical alumina having an outer diameter of5 mm, while the outlet side was filled with 750 ml of Catalyst 2,wherein the length of a catalyst layer was 3005 mm.

The heating medium bath temperature was elevated to a temperature of340° C. at a rate of 50° C./hour, while a gas comprising 9% by volume ofoxygen, 10% by volume of water vapor and 81% by volume of nitrogen waspassed through this catalyst layer at a space velocity of 240 hour⁻¹.

Then, with the heating medium bath temperature maintained at atemperature of 340° C., a gas comprising 2% by volume of tertiarybutanol, 8% by volume of oxygen, 15% by volume of water vapor and 75% byvolume of nitrogen was passed through the catalyst layer at a spacevelocity of 1000 hour⁻¹ for a period of three hours.

Subsequently, with the heating medium bath temperature maintained at atemperature of 340° C., a raw material gas comprising 5% by volume oftertiary butanol, 12% by volume of oxygen, 10% by volume of water vaporand 73% by volume of nitrogen was passed through the catalyst layer at areaction temperature (i. e., a heating medium bath temperature) of 340°C. at a space velocity of 1000 hour⁻¹. When the temperatures of thecatalyst layer were measured at this time, a hot spot having a maximumtemperature was observed at a site located 550 mm apart from the end ofthe inlet side for the raw material gas, wherein ΔT at the maximumtemperature was 32° C. In addition, the rate of reaction of tertiarybutanol was 100.0%, the selectivity factor of methacrolein was 84.0%,the selectivity factor of methacrylic acid was 3.2%, and the yield ofmethacrolein and methacrylic acid was 87.2%.

COMPARATIVE EXAMPLE 6

An oxidation reaction was carried out in a similar manner to that inExample 4, except that the temperature of a heating medium bath waselevated to 340° C. without passing the passing gas after elevating thetemperature, and except that thereafter a raw material gas wasimmediately passed through the catalyst layer. As a result, a hot spothaving a maximum temperature was observed at a site located 450 mm apartfrom the end of the raw material gas inlet side of the catalyst layer,wherein ΔT at the maximum temperature was 44° C. In addition, the rateof reaction of tertiary butanol was 100.0%, the selectivity factor ofmethacrolein was 81.7%, the selectivity factor of methacrylic acid was3.3%, and the yield of methacrolein and methacrylic acid was 85.0%.

EXAMPLE 5

To 1000 parts of water, 500 parts of ammonium paramolybdate, 6.2 partsof ammonium paratungstate, 1.4 parts of potassium nitrate and 212.7parts of silicasol of 20% by mass were added, heated and agitated(Liquid A). Aside from this, to 850 parts of water, 50 parts of nitricacid of 60% by mass were added and homogenized, and then 103.0 parts ofbismuth nitrate were added thereto and dissolved. To the mixture, 114.4parts of ferric nitrate, 274.7 parts of cobalt nitrate, 34.3 parts ofnickel(II) nitrate, 7.0 parts of zinc nitrate and 30.3 parts ofmagnesium nitrate were sequentially added and dissolved (Liquid B).Liquid B was added to Liquid A to form a slurry, and then 10.3 parts ofantimony trioxide were added thereto and heated and agitated, so thatmost of water was evaporated. The resultant caked matter was dried at atemperature of 120° C., and then calcined at a temperature of 500° C.for a period of four hours. To 100 parts of the resultant calcinedproduct, 2 parts of graphite were added, which were then formed intorings having an outer diameter of 4 mm, an inner diameter of 2 mm and alength of 4 mm by using a tablet forming machine, whereby Catalyst 1 wasobtained. The elementary composition of Catalyst 1 comprisedMo₁₂W_(0.1)Bi_(0.9)Fe_(1.2)Co₄Ni_(0.5)Zn_(0.1)Mg_(0.5)Sb_(0.3)K_(0.06)Si₃,except oxygen.

The temperature of a heating medium bath of a tubular type of fixed bedsteel reactor having an inner diameter of 25.4 mm as provided with theheating medium bath was set to a temperature of 180° C., and the inletside for raw material gas was filled with a mixture of 620 ml ofCatalyst 1 and 130 ml of a spherical alumina having an outer diameter of5 mm, while the outlet side was filled with 750 ml of Catalyst 1,wherein the length of a catalyst layer was 3005 mm.

The heating medium bath temperature was elevated to a temperature of310° C. at a rate of 50° C./hour, while a gas comprising 9% by volume ofoxygen, 10% by volume of water vapor and 81% by volume of nitrogen waspassed through this catalyst layer at a space velocity of 240 hour⁻¹.

Then, with the heating medium bath temperature maintained at atemperature of 310° C., a gas (i. e., a passing gas after elevating thetemperature) comprising 2% by volume of propylene, 8% by volume ofoxygen, 15% by volume of water vapor and 75% by volume of nitrogen waspassed through the catalyst layer at a space velocity of 1000 hour⁻¹ fora period of three hours.

Subsequently, with the heating medium bath temperature maintained at atemperature of 310° C., a raw material gas comprising 5% by volume ofpropylene, 12% by volume of oxygen, 10% by volume of water vapor and 73%by volume of nitrogen was passed through the catalyst layer at areaction temperature (i. e., a heating medium bath temperature) of 340°C. at a space velocity of 1000 hour⁻¹. When the temperatures of thecatalyst layer were measured at this time, a hot spot having a maximumtemperature was observed at a site located 500 mm apart from the end ofthe inlet side for the raw material gas, wherein ΔT at the maximumtemperature was 29° C. In addition, the rate of reaction of propylenewas 98.5%, the selectivity factor of acrolein was 88.3%, the selectivityfactor of acrylic acid was 5.8%, and the yield of acrolein and acrylicacid was 92.7%.

EXAMPLE 6

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 2.6% byvolume of propylene, 8% by volume of oxygen, 15% by volume of watervapor and 74.4% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 470 mm apart from theend of the raw material gas inlet side of a catalyst layer, wherein ΔTat the maximum temperature was 31° C. In addition, the rate of reactionof propylene was 98.6%, the selectivity factor of acrolein was 88.1%,the selectivity factor of acrylic acid was 5.8%, and the yield ofacrolein and acrylic acid was 92.6%.

EXAMPLE 7

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the time for passing the passing gas afterelevating the temperature was changed to 1.5 hours. As a result, a hotspot having a maximum temperature was observed at a site located 470 mmapart from the end of the raw material gas inlet side of a catalystlayer, wherein ΔT at the maximum temperature was 31° C. In addition, therate of reaction of propylene was 98.6%, the selectivity factor ofacrolein was 88.1%, the selectivity factor of acrylic acid was 5.8%, andthe yield of acrolein and acrylic acid was 92.6%.

COMPARATIVE EXAMPLE 7

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the temperature of a heating medium bath waselevated to 310° C. without passing the passing gas through a catalystlayer after elevating the temperature, and except that thereafter a rawmaterial gas was immediately passed through the catalyst layer. As aresult, a hot spot having a maximum temperature was observed at a sitelocated 400 mm apart from the end of the raw material gas inlet side ofthe catalyst layer, wherein ΔT at the maximum temperature was 41° C. Inaddition, the rate of reaction of propylene was 98.9%, the selectivityfactor of acrolein was 86.5%, the selectivity factor of acrylic acid was5.0%, and the yield of acrolein and acrylic acid was 90.5%.

COMPARATIVE EXAMPLE 8

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the time for passing the passing gas afterelevating the temperature was changed to ten minutes. As a result, a hotspot having a maximum temperature was observed at a site located 400 mmapart from the end of the raw material gas inlet side of the catalystlayer, wherein ΔT at the maximum temperature was 40° C. In addition, therate of reaction of propylene was 98.7%, the selectivity factor ofacrolein was 86.7%, the selectivity factor of acrylic acid was 5.1%, andthe yield of acrolein and acrylic acid was 90.6%.

COMPARATIVE EXAMPLE 9

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 4.5% byvolume of propylene, 12% by volume of oxygen, 10% by volume of watervapor and 73.5% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of the catalyst layer, wherein ΔTat this maximum temperature was 41° C. In addition, the rate of reactionof propylene was 98.9%, the selectivity factor of acrolein was 86.5%,the selectivity factor of acrylic acid was 5.0%, and the yield ofacrolein and acrylic acid was 90.5%.

COMPARATIVE EXAMPLE 10

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 0.6% byvolume of propylene, 8% by volume of oxygen, 15% by volume of watervapor and 76.4% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of the catalyst layer, wherein ΔTat this maximum temperature was 40° C. In addition, the rate of reactionof propylene was 98.7%, the selectivity factor of acrolein was 86.7%,the selectivity factor of acrylic acid was 5.1%, and the yield ofacrolein and acrylic acid was 90.6%.

COMPARATIVE EXAMPLE 11

An oxidation reaction was carried out in a similar manner to that inExample 1, except that the composition of the gas as passed when thetemperature of a heating medium bath was elevated to 310° C. was changedto the one comprising 2% by volume of propylene, 8% by volume of oxygen,15% by volume of water vapor and 75% by volume of nitrogen. As a result,a hot spot having a maximum temperature was observed at a site located550 mm apart from the end of the raw material gas inlet side of acatalyst layer, wherein ΔT at this maximum temperature was 20° C. Inaddition, the rate of reaction of propylene was 94.7%, the selectivityfactor of acrolein was 88.0%, the selectivity factor of acrylic acid was5.6%, and the yield of acrolein and acrylic acid was 88.6%. From theresults, it is considered that the catalyst was poisoned when thetemperature thereof was elevated, because ΔT at the hot spot wasdecreased as compared to the one in Example 1 while the rate of reactionof propylene also was decreased.

EXAMPLE 8

To 1000 parts of water, 500 parts of ammonium paramolybdate, 12.3 partsof ammonium paratungstate and 1.4 parts of potassium nitrate were added,heated and agitated, and thereafter a solution in which 4.1 parts of 85%by mass phosphoric acid is dissolved in 100 parts of water was addedthereto, and further heated and agitated (Liquid C). Aside from this, to850 parts of water, 50 parts of nitric acid of 60% by mass were addedand homogenized, and then 114.5 parts of bismuth nitrate were addedthereto and dissolved. To the mixture, 143.0 parts of ferric nitrate,309.0 parts of cobalt nitrate, 7.0 parts of zinc nitrate, 3.2 parts ofsilver nitrate and 6.1 parts of magnesium nitrate were sequentiallyadded and dissolved (Liquid D). Liquid D was added to Liquid C to form aslurry, and then heated and agitated, so that most of water wasevaporated. The resultant caked matter was dried at a temperature of130° C., and then calcined at a temperature of 300° C. in an atmosphereof air for a period of one hour, and pulverized. To 100 parts of theresultant pulverized product, 2 parts of graphite were added and mixed,which were then formed into rings having an outer diameter of 4 mm, aninner diameter of 2 mm and a length of 4 mm by using a tablet formingmachine. This formed tablet product was calcined at a temperature of500° C. in an atmosphere of air for a period of six hours, wherebyCatalyst 2 was obtained. The elementary composition of Catalyst 2comprisedMo₁₂W_(0.2)Bi₁Fe_(1.5)P_(0.15)Ag_(0.08)Co_(4.5)Zn_(0.1)Mg_(0.1)K_(0.06),as an atomic ratio except oxygen.

The temperature of a heating medium bath of a tubular type of fixed bedsteel reactor having an inner diameter of 25.4 mm as provided with theheating medium bath was set to a temperature of 180° C., and the inletside for raw material gas was filled with a mixture of 620 ml ofCatalyst 2 and 130 ml of a spherical alumina having an outer diameter of5 mm, while the outlet side was filled with 750 ml of Catalyst 2,wherein the length of a catalyst layer was 3005 mm.

The heating medium bath temperature was elevated to a temperature of310° C. at a rate of 50° C./hour, while a gas comprising 9% by volume ofoxygen, 10% by volume of water vapor and 81% by volume of nitrogen waspassed through this catalyst layer at a space velocity of 240 hour⁻¹.

Then, with the heating medium bath temperature maintained at atemperature of 310° C., a gas comprising 2% by volume of propylene, 8%by volume of oxygen, 15% by volume of water vapor and 75% by volume ofnitrogen was passed through the catalyst layer at a space velocity of1000 hour⁻¹ for a period of three hours.

Subsequently, with the heating medium bath temperature maintained at atemperature of 310° C., a raw material gas comprising 5% by volume ofpropylene, 12% by volume of oxygen, 10% by volume of water vapor and 73%by volume of nitrogen was passed through the catalyst layer at areaction temperature (i. e., a heating medium bath temperature) of 310°C. at a space velocity of 1000 hours⁻¹. When the temperatures of thecatalyst layer were measured at this time, a hot spot having a maximumtemperature was observed at a site located 550 mm apart from the end ofthe inlet side for the raw material gas, wherein ΔT at the maximumtemperature was 32° C. In addition, the rate of reaction of propylenewas 99.0%, the selectivity factor of acrolein was 89.0%, the selectivityfactor of acrylic acid was 6.2%, and the yield of acrolein and acrylicacid was 94.2%.

COMPARATIVE EXAMPLE 12

An oxidation reaction was carried out in a similar manner to that inExample 4, except that the temperature of a heating medium bath waselevated to 310° C. without passing the passing gas after elevating thetemperature, and except that thereafter a raw material gas wasimmediately passed through the catalyst layer. As a result, a hot spothaving a maximum temperature was observed at a site located 450 mm apartfrom the end of the raw material gas inlet side of the catalyst layer,wherein ΔT at the maximum temperature was 44° C. In addition, the rateof reaction of propylene was 99.4%, the selectivity factor of acroleinwas 86.5%, the selectivity factor of acrylic acid was 5.9%, and theyield of acrolein and acrylic acid was 91.8%.

INDUSTRIAL APPLICABILITY

According to the method for producing methacrolein and/or methacrylicacid by subjecting isobutylene and/or tertiary butanol to a vapor-phasecatalytic oxidation with molecular oxygen in the presence of a solidoxidation catalyst in a tubular type of fixed bed reactor, of thepresent invention, a temperature of a hot-spot zone can be sufficientlycontrolled, whereby methacrolein and methacrylic acid can be producedwith a high yield.

Furthermore, the use of the compound oxide represented by theabove-mentioned formula (1) as the solid oxidation catalyst furtherenhances the yield of methacrolein and methacrylic acid.

According to the method for producing acrolein and/or acrylic acid bysubjecting propylene to a vapor-phase catalytic oxidation with molecularoxygen in the presence of a solid oxidation catalyst in a tubular typeof fixed bed reactor, of the present invention, a temperature of ahot-spot zone can be sufficiently controlled, whereby acrolein andacrylic acid can be produced with a high yield.

Furthermore, the use of the compound oxide represented by theabove-mentioned formula (2) as the solid oxidation catalyst furtherenhances the yield of acrolein and acrylic acid.

1. A method for producing methacrolein and/or methacrylic acid bypassing a raw material gas comprising isobutylene and/or tertiarybutanol and oxygen through a catalyst layer in a tubular type of fixedbed reactor which is filled with a solid oxidation catalyst, whichcomprises passing a gas comprising isobutylene and/or tertiary butanolin a concentration lower than that of said raw material gas, and oxygenthrough said catalyst layer for a period of one hour or more prior topassing said raw material gas through said catalyst layer.
 2. A methodfor producing methacrolein and/or methacrylic acid, which comprises:filling a tubular type of fixed bed reactor with a solid oxidationcatalyst; elevating a temperature of the resultant catalyst layer to arange of 250° C. to 400° C. while passing a gas including oxygen,nitrogen, water vapor and 0 to 0.5% by volume of isobutylene and/ortertiary butanol through said catalyst layer; passing a gas including 1to 3.8% by volume of isobutylene and/or tertiary butanol, 7 to 16% byvolume of oxygen and 5 to 50% by volume of water vapor through saidcatalyst layer at a temperature of 250° C. to 400° C. for a period ofone hour or more; and thereafter passing a raw material gas including 4to 9% by volume of isobutylene and/or tertiary butanol, 7 to 16% byvolume of oxygen and 5 to 50% by volume of water vapor through saidcatalyst layer at a temperature of 250° C. to 400° C.
 3. The method forproducing methacrolein and/or methacrylic acid according to claim 1 or2, wherein said solid oxidation catalyst is a compound oxide representedby the following formula (1):Mo_(a)Bi_(b)Fe_(c)A_(d)X_(e)Y_(f)Z_(g)O_(h)  (1) wherein Mo, Bi, Fe andO represent molybdenum, bismuth, iron and oxygen, respectively; Arepresents nickel and/or cobalt; X represents at least one elementselected from the group consisting of magnesium, zinc, chromium,manganese, tin and lead; Y represents at least one element selected fromthe group consisting of phosphorus, boron, sulfur, tellurium, silicon,germanium, cerium, niobium, titanium, zirconium, tungsten and antimony;Z represents at least one element selected from the group consisting ofpotassium, sodium, rubidium, cesium and thallium; and each of a, b, c,d, e, f, g and h represents an atomic ratio of each element, wherein0.1≦b≦5, 0.1≦c≦5, 1≦d≦12, 0≦e≦10, 0≦f≦10 and 0.01≦g≦3 when a=12, and hmeans an atomic ratio of oxygen necessary to satisfy the atomic valenceof each of said elements.
 4. A method for producing acrolein and/oracrylic acid by passing a raw material gas comprising propylene andoxygen through a catalyst layer in a tubular type of fixed bed reactorwhich is filled with a solid oxidation catalyst, which comprises passinga gas comprising propylene in a concentration lower than that of saidraw material gas, and oxygen through said catalyst layer for a period ofone hour or more prior to passing said raw material gas through saidcatalyst layer.
 5. A method for producing acrolein and/or acrylic acid,which comprises: filling a tubular type of fixed bed reactor with asolid oxidation catalyst; elevating a temperature of the resultantcatalyst layer to a range of 250° C. to 400° C. while passing a gasincluding oxygen, nitrogen, water vapor and 0 to 0.5% by volume ofpropylene through said catalyst layer; passing a gas including 1 to 3.8%by volume of propylene, 7 to 16% by volume of oxygen and 5 to 50% byvolume of water vapor through said catalyst layer at a temperature of250° C. to 400° C. for a period of one hour or more; and thereafterpassing a raw material gas including 4 to 9% by volume of propylene, 7to 16% by volume of oxygen and 5 to 50% by volume of water vapor throughsaid catalyst layer at a temperature of 250° C. to 400° C.
 6. The methodfor producing acrolein and/or acrylic acid according to claim 4 or 5,wherein said solid oxidation catalyst is a compound oxide represented bythe following formula (2):Mo_(a′)Bi_(b′)Fe_(c′)A′_(d′)X′_(e′)Y′_(f′)Z′_(g′)Si_(h′)O_(i)  (2)wherein Mo, Bi, Fe, Si and O represent molybdenum, bismuth, iron,silicon and oxygen, respectively; A′ represents nickel and/or cobalt; X′represents at least one element selected from the group consisting ofmagnesium, zinc, chromium, manganese, tin, strontium, barium, copper,silver and lead; Y′ represents at least one element selected from thegroup consisting of phosphorus, boron, sulfur, tellurium, aluminum,gallium, germanium, indium, lanthanum, cerium, niobium, tantalum,titanium, zirconium, tungsten and antimony; Z′ represents at least oneelement selected from the group consisting of potassium, sodium,rubidium, cesium and thallium; each of a′, b′, c′, d′, e′, f′, g′, h′and i represents an atomic ratio of each element, wherein 0.01≦b′≦5,0.01≦c′≦5, 1≦d′≦12, 0≦e′≦10, 0≦f′≦10, 0.001≦g′≦3 and 0≦h′≦20 when a′=12,and i means an atomic ratio of oxygen necessary to satisfy the atomicvalence of each of said elements.